简述出生后血循环的改变。
参考答案：
（1）肺循环压力下降。（2）左心房压力增高。（3）卵圆孔功能性关闭。（4）动脉导管功能性关闭。（5）脐血管形成韧带。
双晶要素
Did your father tell you ______?
A．when he travelled to Hong Kong
B．how he goes to Shanghai
C．where he has spent his holidays
D．why did he visit Hangzhou
